In a Mobile Softswitch-based Core Network, each Time Division Multiplex (TDM) resource (e.g. an E1) in a Media Gateway is statically allocated to one Mobile Switching Centre (MSC) Server. MSCs can be pooled in order to improve the resilience of a network in the event of failure of one MSC. In an MSC pool, the result of this is that TDM resources per MSC Server must be over-allocated to deal with situations when an MSC Server in the pool is out-of-service (e.g. owing to maintenance or faults), and other MSC Servers in the pool are required to handle the traffic normally handled by the out-of-service MSC Server. This over-allocation results in a high capital and operating expenditure for network operators. The TDM resources in question are used both on the A-interface and the Point-of-Interconnect (POI) towards other networks. Another problem in an MSC Pool is the handling of the POI interface from a signalling point of view. In order to keep the number of MSC Servers visible on the POI as low as possible, a normal recommendation is to dedicate two MSC Servers to act as gateways. The result of this is that normally two MSC Servers (i.e, the originating and the gateway) are involved in an originating call. The over-allocation of TDM resources is 50% on the POI in this configuration.
The problem of over-allocation of TDM resources is illustrated in FIG. 1. Each MSC-S 101, 102, 103 owns dedicated Circuit Identification Codes (CICs) 104, 105, 106, and if one MSC-S 101 fails than the other MSC-Ss 102, 103 must handle traffic. In normal operation, 50% of the CICs are never used, and all MSC-S nodes are visible to other networks.
Referring to FIG. 2 herein, a problem of MSC-S (numbered as 1-4) SS7 point codes being visible in external networks is illustrated. This complicates or hinders MSC Pool expansions with new MSC Servers and in some cases costs extra money for the operators as public SS7 Point Codes are needed.
Referring to FIG. 3, when an MSC-S (e.g. MSC-S 1) become unavailable for some reason, such as failure or maintenance, the TDM Resources assigned to the unavailable MSC-S 1 remain unavailable as described above. In a layered architecture, the physical TDM Resources are terminated by the Media Gateways 5, but they are controlled by the dedicated MSC-Ss. Thus the actual TDM Resources are not lost and the transmission capacity could be still used. This lowers the capacity of the network until the owner of the TDM resources recovers.
Referring to FIG. 4, when the MSC Pool 6 is directly connected to the Point of interface (POI), dimensioning the required TDM resources is difficult, because subscriber behaviour might not exactly the same in each MSC Pool Member 1-4. Therefore additional TDM resources must be reserved towards the POI interface to avoid networks congestion. In the example of FIG. 4, MSC-S 1 has congestion even though 15% of E1s are free.